Adverse drug reactions (ADRs) are a major cause of morbidity and mortality in children. Current models of ADR surveillance have repeatedly demonstrated little pragmatic value to practicing clinicians. ADR reporting rates in the US and Canada suggest that only 5% of ADRs are reported. The Genotypic Approaches to Therapy in Children (GATC) network was established to identify and solve drug safety problems in paediatrics. We hypothesized that genetic polymorphisms underlie a significant portion of concentration-dependent ADRs in children. Our objective was to establish an ADR active surveillance network in paediatric hospitals across Canada. Surveillance clinicians evaluate clinical information from ADR cases and drug-matched controls, and collected DNA samples from all patients. The surveillance network will enable the identification of predictive genomic-markers for ADRs. With this knowledge, children at risk can be identified before therapy is initiated and enable personalized adjustments to therapy based on genetic make-up.